(1) Field of the Invention
The present invention relates generally to a system and method for automatically controlling a vehicle speed to a desired cruise speed applicable to vehicles.
(2) Description of the Background Art
A system for automatically controlling a vehicle speed to a desired cruise speed includes a vehicle speed setting switch group having a set switch, an acceleration switch, and a resume switch and a microcomputer which compares a target vehicle speed set by the vehicle speed setting switch with an actual vehicle speed detected by a vehicle speed sensor and adjusts a fuel supply quantity (an opening angle of an engine throttle valve) supplied to a vehicular engine so that the vehicle runs at the set vehicle speed and maintains the vehicle speed thereat. In addition, a plurality of cancel switches such as a brake switch are provided to cancel the cruise run operation of the above-described system.
The microcomputer serves as a control portion of the cruise speed controlling system. The control portion is reset when a power supply of the above-described system is turned on so that a storage of the control portion in which the previously set vehicle speed is stored is cleared for safe operation of the vehicle.
Thereafter, the control portion accepts an input vehicle set speed signal derived from the vehicle speed setting switch.
Such a cruise speed controlling system as described above is exemplified by a Japanese Patent Application Second Publication (Non-examined) No. Showa 62-34224 published on July 24, 1987.
However, since the above-described system accepts the incoming vehicle speed setting signal derived from the vehicle speed setting switch group after the control portion is reset, the control portion operates for the vehicle to run at a cruise speed in the control portion immediately after the reset when any one switch of the vehicle speed setting switch group is turned on or remains on due to some failure. For example, when the acceleration switch remains on when the power supply is turned on due to some failure, the control portion operates for the vehicle to accelerate.